Effect Of Graphene Oxide On Mechanical Properties Of Interface Transition Zone Of Recycled Concrete

In recent years,the rapid development of China's construction industry and the scientific requirements for reducing consumption and reducing emissions have led many scholars and engineers to conduct a lot of research on the efficient use of waste concrete.Recycled concrete has higher non-uniformity and complex internal microstructure than ordinary concrete.Interfacial transition zone is the weak position of recycled concrete.Changing the microstructure of concrete and weakening the interface transition zone can improve its macroscopic performance.In this paper,the influence of graphene oxide on the mechanical properties of the transition zone of recycled concrete and its mechanism are discussed,which provides a reference for the study of macroscopic mechanical properties of recycled concrete.The micro-mechanical properties and microstructure of the interfacial transition zone of graphene oxide recycled concrete under conventional conditions and freeze-thaw cycles were studied by means of nanoindenter and scanning electron microscope,so as to understand the elastic mode of graphene oxide on different interface regions of recycled concrete.The variation of the magnitude and the width of the interface transition zone.The experimental results show that the addition of graphene oxide under normal conditions makes the elastic modulus of the recycled concrete LJ-XJ interface and LG-XJ interface increase to different degrees,the interface area width decreases and the effect on the LJ-XJ interface is more obvious;Electron microscopy showed that the microstructure of the transition zone of the graphene oxide-recycled concrete was more encrypted,the crystal family arrangement became more disordered,the new slurry was more closely connected with the old aggregate,and the micro-cracks at the junction of the new and old slurry were reduced.The rate is reduced.After 100 freeze-thaw cycles,the mechanical properties of graphene oxide-recycled concrete and ordinary recycled concrete decreased to varying degrees.The water in the concrete micropores alternated between positive and negative temperatures,which caused tensile stress in the concrete.The crack eventually causes the concrete surface to peel off until it breaks.The interfacial transition zone of graphene oxide recycled concrete is lower than that of ordinary recycled concrete,and the volume ratio of high-density hydrated calcium silicate phase increases,which reduces the area of concrete directly in contact with water and contacts the elastic modulus and hardness of part of concrete.The improvement weakens the freeze-thaw damage and improves the frost resistance,so the graphene oxide recycled concrete has a lower degree of mechanical performance degradation than the ordinary recycled concrete.From the relationship between the micromechanical properties and the macroscopic mechanical properties of recycled concrete,it can be obtained that graphene oxide can enhance and improve the mechanical properties and microstructure of the transition zone between new and old interfaces of recycled concrete,thereby improving and improving the macroscopic mechanical properties of recycled concrete.